1. Field of the Invention
The invention relates to a retroreflector or a retroreflector arrangement assembled from a plurality of retroreflectors and having structures for heating the faces of the retroreflector.
2. Description of Related Art
A retroreflector is an optical component comprised of a triple-mirror prism. A triple-mirror prism has three prism faces, which are at right angles to one another, that form a three-dimensional cube corner. Each of these prism faces constitutes a right-angled, isosceles triangle. The fourth limiting face of such a triple-mirror prism is an equilateral triangle. This face serves as the entrance and exit, simultaneously, for a light beam. Every beam entering the triple-mirror prism from outside is totally reflected at all three (isosceles) faces and exits the triple-mirror prism parallel to its direction of incidence and exits symmetrically to the central beam. When the triple-mirror prism is rotated about an arbitrary axis, the direction of the retroreflected beam is not changed.
Such retroreflectors are used in many fields of optics, for example, they are used frequently in optical surveying of open terrain. Difficulty arises, however, because, during operation of the retroreflector, weather conditions often have an adverse impact on the retroreflector's accuracy and performance.
The difficulties suggested in the preceding are not intended to be exhaustive, but are among many which tend to reduce the effectiveness of retroreflectors. Other noteworthy problems may exist; however, those presented above should be sufficient to demonstrate that such methods and apparatuses appearing in the past will admit to worthwhile improvement.